Glass cathode-ray tube for the reproduction of images



Sept. 14, 1965 M. STEL 3,206,056

GLASS CATHODE-RAY TUBE FOR. THE REPRODUCTION OF IMAGES Filed Nov. 24, 1961 FIG.2

INVENTOR MARINUS STEL AGENT United States Patent 3,206,056 GLASS CATHODE-RAY TUBE FOR THE REPRODUCTION OF IMAGES Marinus Stel, Emmasingel, Eindhoven, Netherlands, as-

signor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Nov. 24, 1961, Ser. No. 154,611 Claims priority, application Netherlands, Dec. 9, 1960, 258,914 5 Claims. (Cl. 220-2t1) The invention relates to glass cathode-ray tubes for the reproduction of images, particularly large size tubes and more particularly television display tubes.

With such cathode-ray tubes damage or ageing of the glass may give rise to implosion; particularly with large size display tubes this may have serious consequences for persons standing near, while material damage may also be great. This applies particularly to tubes having a principally rectangular window.

In many ways efforts have been made to reduce the consequences of implosion or to minimize the risk of implosion.

In order to reduce the consequences of implosion, a protective plate usually is arranged in front of the display window in the cabinet of the apparatus in which the cathode-ray tube is housed. However, this is not eificaceous for the protection of those who are in charge of mounting the apparatus.

It is furthermore known to cover the window, and

as the case may be, also the cone of a cathode-ray tube with a synthetic substance layer, so that in the event of implosion the fragments are held together. The synthetic substance may be applied in the form of a hood to the window and the adjacent part of the cone and be shrunk thereon. Since, in general, in the transitional zone between the window and the cone and in a strip around the image surface of the'window, subsequent to exhausting, tensile stress may occur in the glass, ageing phenomena may occur in the glass of this zone, so that at his place the risk of a break-down of the glass is at a maximum.

It has been found that the known expedients are, indeed, capable of materially reducing the consequences of implosion, but they require a synthetic substance layer on the whole image surface. A synthetic substance suitable for the said purpose, however, usually tends to discolor, it can be easily scratched, and it is soon stained by smoke and dust particles.

It has been found possible to suppress the risk of implosion substantially completely and, at any rate, to render the consequence of an implosion quite harmless by embedding an elastic tissue in the synthetic substance layer, which is applied at least partly to the glass wall of a cathode-ray image reproducing tube, in accordance with the invention at least as far as the said layer covers the zone adjacent the image surface of the window and extends over part of the cone, the said tissue being stretched as a stocking around the said zone.

It has been found that even if mechanically a crack is made in the glass wall, this crack surprisingly does not travel further. This is even the case with a crack produced in the image surface of the window not covered by the tissue-containing layer. Then the vessel slowly draws in air. It is, however, important that the synthetic substance layer should satisfactorily adhere to the glass. To this end, if desired, the glass may be previously coated with a separate intermediate layer of a substance having greater adhesive power both for the glass'and the tissue-containing synthetic layer than the tissue-containing synthetic layer for the glass, so that the intermediate layer has the function of a glue.

The tissue-containing synethetic layer according to the invention contains preferably a round-knitted tricot tissue, for example, of glass thread; however, if desired, elastic tissues of other material may be used, for example a tissue of metal wires. Moreover, the elastic tissue need not be round-knit, it may consist of a rounded strip of which the ends are stuck to each other, for example by sewing, sealing or gluing. Apparently the addition of the tissue improves the rigidity of the synthetic layer to an extent such that the glass parts can no longer diverge, so that a crack cannot propagate.

Since the said layer is opaque, it can, of course, not be applied to the image surface of the window. It has been found, that this is not necessary, since the very presence of such a layer on the zone beyond the image surface, where tensile stress may occur in the glass, suffices for obtaining the desired effect also in the image surface.

A clear intermediate layer applied to the glass for improving the adhesion may serve, in addition, if desired to obtain, in known manner, certain optical effects, such as the suppression of reflections from the light sources in the surroundings or to increase the contrast. The tissue-containing layer according to the invention may furthermore be used in conjunction with means for reinforcing the surface of the glass itself, for example for applying a glaze layer. The image surface is to be understood to mean the window part employed for image display. This surface is usually determined by the luminescent layer on the inner side, but often also by a mask on the outer side, which mask may be arranged on the tube or in the cabinet of the apparatus or, as in the present case, may be formed by the tissue-containing layer.

The invention will now be described more fully with reference to the drawing in which FIGS. 1 and 2 shows different embodiments of cathoderay tubes according to the invention.

Referring to FIG. 1, reference numeral 1 designates the cone of a cathode-ray tube, to which a neck 2 and a display window 3 are sealed, to which window 3 the luminescent screen 8 is applied on the inner side. In the zone 4 tensile stress is likely to occur in the glass. In accordance with the invention at least the part of this zone 4 adjacent the image surface is covered with a rigid synthetic substance layer 5 of a few millimeters in thickness, which consists of a preferably round-knitted tissue of glass fibre, impregnated with a hardened polyester resin, which adheres satisfactorily to the glass, for example an unsaturated polyester, which is dissolved prior to the application in, for example, styrene. This resin may, for example, be applied by spraying to the tissue and the glass surface. The tricot tissue stocking, before it is arranged around the zone to be covered of a 23 cone of a cathode-ray tube has a circumference of 65 to 70 cms. The maximum circumference of a 23" bulb at the area of the zone to be covered amounts to cms. This ratio, however, is not critical at all.

After the tricot tissue has been arranged around the bulb, an unsaturated polyesters resin is sprayed onto it, until the tissue is completely embedded in this synthetic substance.

The unsaturated polyester may be obtained by polycondensation of an wit-unsaturated dicarboxylic acid and a polyvalent alcohol. The polyester may, if desired, be modified by saturated and/or halogen containing dicarboxylic acids. Suitable polyvalent alcohols are, for example, glycol or glycerol.

Use may be made successfully of solutions of 50 to 70% by weight of unsaturated polyester in styrene.

Hardening may be carried out under the action of combinations known to this end of catalysts such as benzyl peroxide, methyl ethylketone peroxide and the like and accelerators such as cobalt-naphthenate or dimethylaniline.

In order to avoid premature hardening of the polyester, a solution of the catalyst in part of the polyester styrene mixture may be mixed, just before the synthetic substance is applied, with a solution of the hardening accelerator in the remainder of the polyester-styrene mixture.

The unsaturated polyester solution may furthermore contain, if desired, apart from coloring substances and pigments, filling substances such as titanium dioxide (TiO in order to avoid shrinkage and cracking of the layer during hardening.

The elastic glass fibre tissue may be made from a substantially arbitrary, readily workable kind of glass. Very suitable kinds are glass having a low alkali content.

It has been found not to be necessary to restrict the image surface to the space lying within the zone where tensile stress may occur in the glass. Covering part of this zone at the area of the strongly curved transition between image surface and sealing area of the cone will, in general, be sufiicient.

From FIG. 2 it appears that the bulb is previously coated with a satisfactorily adhereing intermediate layer 7, for example, of polyvinylacetate, on which an elastic, round-knitted strip of glass fibre is arranged, by slipping it in the elongated state around the bulb, so that the tissue shrinks tightly around it and provides an intimate contact in spite of the irregular shape of the bulb. Then this tissue is impregnated with the synthetic substance layer 5 by spraying the synthetic substance.

If desired, the synthetic layer may, in addition, serve to provide the bulb with ears for fastening the tube in the cabinet of the apparatus.

It is furthermore possible to reduce materially the wall thickness of the bulbs and hence to use a tube of markedly lighter weight, since on the one hand the rigidity of the bulb is improved by the coating according to the invention and, on the other hand, the safety factor can be chosen to be much lower since implosion or breakdown of the bulb is thus rendered quite harmless.

If the outer side of the cone is furthermore to be coated with a conductive layer, this layer may be applied to the synthetic substance layer. However, as an alternative,

the synthetic substance layer itself may be rendered conductive by the addition of metal or graphite particles or, when a non-conductive, elastic tissue is used, by providing a conductive metal network in the synthetic substance layer. The tissue may furthermore consist half of metal wires and half of non-metallic wires, forexample glass fibre.

What is claimed is:

1. A cathode-ray tube comprising a glass window portion covered in partwith a luminescent layer and an adjoining glass cone portion, and an implosion-preventing layer covering par-t of the external surface of said cone portion and extending. only to the part of the window portion covered with the luminescent layer, said implosion-preventing layer consisting of an originally elastic stretched inorganic tissue embedded in a non-elastic synthetic resin.

2. A cathode-ray tube as claimed in claim 1, in which between the tissue-containing synthetic resin layer and the glass an intermediate layer is provided for improving the adhesion of the tissue-containing synthetic resin layer to the glass.

3. A cathode-ray tube as claimed in claim 1, in which the tissue consists of glass fibre.

4. A cathode-ray tube as claimed in claim 1, in which the tissue consists at least partly of metal wire.

5. A cathode-ray tube as claimed in claim 1, in which at least the zone adjacent the image surface in the winilow and the cone is covered with the tissue-containing ayer.

References Cited by the Examiner UNITED STATES PATENTS 2,293,529 8/42 Bedford 31392 X 2,614,058 10/52 Francis.

2,734,142 2/56 Barnes 313-92 2,785,820 3/57 Vincent et a1 220-21 FOREIGN PATENTS 22,398 4/35 Australia.

THERON E. CONDON, Primary Examiner.

ARTHUR GAUSS, Examiner. 

1. A CATHODE-RAY TUBE COMPRISING A GLASS WINDOW PORTION COVERED IN PART WITH A LUMINESCENT LAYER AND AN ADJOINING GLASS CONE PORTION, AND AN IMPLOSION-PREVENTING LAYER COVERING PART OF THE EXTERNAL SURFACE OF SAID CONE PORTION AND EXTENDING ONLY TO THE PART OF THE WINDOW PORTION COVERED WITH THE LUMINESCENT LAYER, SAID IMPLOSION-PREVENTING LAYER CONSISTING OF AN ORIGINALLY ELASTIC STRETCHED INORGANIC TISSUE EMBEDDED IN A NIN-ELASTIC SYNTHETIC RESIN. 